The semiconductor industry is increasingly moving to substrates comprising low-k dielectric materials in order to achieve continued scaling of microelectronic devices. Low-k dielectric materials are characterized by having a low dielectric constant relative to silicon dioxide, a common dielectric material. As microelectronic devices become smaller, the amount of dielectric material isolating conductive areas becomes correspondingly smaller. In some conventional examples utilizing silicon dioxide, thinning dielectric material may result in capacitive effects, cross-talk effects, and other undesirable effects that adversely affect device performance. Replacing silicon dioxide with low-k dielectric material of like thickness may reduce or eliminate these detrimental effects.
Use of low-k dielectric materials, however, is not a panacea. For example, some portions of low-k dielectric materials (e.g., trace NH(x) groups), may adversely affect chemistries of subsequent substrate processing. In addition, many low-k dielectric materials lack functional groups, which may be required for covalent chemistry. Furthermore, low-k dielectric materials are characteristically hydrophobic, which makes surfaces of low-k dielectric materials difficult to wet. In some examples, this hydrophobic characteristic may inhibit or altogether prevent aqueous (wet) processing steps from reacting with conductive regions (i.e., copper lines) that may be located directly adjacent with hydrophobic low-k dielectric materials. Some aqueous steps may include: aqueous cleaning steps, metallization steps, and other similar wet steps. While a hydrophobic characteristic may be problematic for featureless substrates, it is especially problematic for substrates having narrow topographical features such as vias and trenches.
For example, surface characteristics of patterned substrates, as may be appreciated, may present challenges to process integration in a manufacturing context. Where wet chemistries are utilized, a hydrophobic dielectric surface having a high wetting angle characteristic may adversely affect adjoining conductive surfaces targeted by the wet chemistries. FIG. 1A is a prior art illustrative cross-sectional view of a portion of a substrate 100A having a base layer 105A, conductive regions 110A, and dielectric regions 120A with arrows 150A illustrating hydrophobic forces at the surface of the dielectric regions 120A. The arrows 150A illustrated in FIG. 1A illustrate the outward force of the hydrophobic properties of the low-k dielectric in dielectric regions 120A. Hydrophobic properties may present challenges in process integration when utilizing aqueous semiconductor processes. In particular, when features are densely integrated having dielectric regions closely interleaved with conductive regions, dielectric regions having hydrophobic properties may hinder or altogether prevent aqueous reactions along conductive regions. One possible adverse result due to hydrophobic characteristics is that deposition rates may not be uniform or, in some example, may fail entirely on smaller more isolated features. Non-uniform thicknesses of deposited layers or failure to deposit layers may cause integration problems during subsequent semiconductor processing as well as performance problems (e.g., increased resistance in thinner depositions) when using a finished device.
FIG. 1B is a prior art illustrative cross-sectional representation of an untreated substrate 100B after a wet deposition process. As illustrated, substrate 100B may include a base layer 105B, dielectric regions 120B, and conductive regions 110B and 112B. A single layer is illustrated, but embodiments provided herein may equally apply to one or many layers without departing from the present invention. In some embodiments, substrate 100B may include an electronic device and may be made, in whole or in functionally significant part, of semiconductor material or materials. As illustrated, conductive regions 110B and 112B and dielectric regions 120B are formed over base 105B, which may be conductive in some embodiments. Thus, for example, conductive regions 110B and 112B may form interconnections between base 105B and other electrically conductive materials subsequently formed as part of substrate 100B. Further, as illustrated, dielectric regions 120B represent areas having hydrophobic characteristics as indicated by arrows 150B. Hydrophobic characteristics may present challenges in process integration when using aqueous semiconductor processes. In particular, when features are densely integrated having dielectric regions closely interleaved with conductive regions, or when features are small or isolated, dielectric regions having hydrophobic characteristics may hinder or altogether prevent aqueous reactions along conductive regions. Thus, one result of these hydrophobic characteristics is that depositions 114B and 116B may not have a uniform thickness, as illustrated, or may not even occur on the smaller more isolated features. Non-uniform thicknesses of deposited layers or failure to deposit may cause integration problems during subsequent semiconductor processing as well as performance problems (e.g., increased resistance in the thinner deposition 116B) when using a finished device. It should be noted that the illustrated thicknesses are not drawn to scale and should not be construed as limiting with respect to scale or proportion.
In other examples, at least some low-k dielectric materials are porous. Porous low-k dielectric materials may, in some examples, trap unwanted materials (such as particles, solvents, etc. . . . ) that may adversely affect dielectric properties. During processing, dielectric surfaces may be subjected to undesirable penetration of damaging process chemistries into underlying dielectric regions. In some cases, capacitance of the dielectric region may be adversely affected. The low-k dielectric material may be physically damaged, degraded, or chemically altered in such a way that the dielectric constant of the material is increased. For example, one class of process chemistries which are particularly reactive with dielectric materials are surfactants. Surfactants, as may be appreciated, are wetting agents that may be utilized to lower the surface tension of a liquid and to allow easier spreading thus improving reactivity of aqueous chemistries. However, surfactants may also have damaging effects. In some examples a dielectric constant of a low-k dielectric material may be temporarily or permanently altered. As may be appreciated, porous low-k dielectric materials include pores that function to lower the dielectric constant of a dielectric material. Certain processing materials such as surfactants may enter and fill the pores of the dielectric material changing the dielectric constant of the dielectric.